1. Field of the Invention
The present invention relates to a vane pump having a main discharge channel and a subsidiary discharge channel, capable of performing discharge from both the main discharge and subsidiary discharge channels when at low pressure and of performing discharge from the main discharge channel only when at high pressure, and capable of reducing the rotational resistance due to the vanes in a state of main discharge only at high pressure.
2. Description of the Related Art
There are vane pumps which have two discharge channels, and which switch to both or one of the channels by a control valve, when at low pressure and high pressure. Japanese Patent Application Publication No. 2005-120894 discloses a vane pump of this kind. The contents of Japanese Patent Application Publication No. 2005-120894 will be described briefly here. The numerals in brackets are those used in Japanese Patent Application Publication No. 2005-120894.
In the vane pump according to Japanese Patent Application Publication No. 2005-120894, intake and discharge is repeated two times during one revolution. In other words, a configuration in which there are two pumps (discharge sources) is achieved. There are two each of the intake ports (221, 222), discharge ports (231, 232) and discharge channels (25, 26), etc.
The intake channel (24) is one channel that is shared by two pumps. In order to distinguish the two pump configurations in the present description, the pump on the right hand-side which performs discharge without passing the spool valve (30) and which is illustrated in FIG. 12 in Patent Document 1 is defined as the main pump, and the pump on the left hand-side which performs discharge via the spool valve (30) and which is illustrated in FIG. 12 is defined as the subsidiary pump, for the sake of convenience.
In FIG. 12A of Japanese Patent Application Publication No. 2005-120894, oil discharged from the subsidiary pump on the left hand-side traverses the spool valve (30), and merges with the oil discharged from the main pump. Therefore, since the oil is discharged from both the main and subsidiary pumps, then it is possible to raise the discharge pressure. This is one example of an operation when the pump is below a prescribed speed of revolution.
In FIG. 12B of Japanese Patent Application Publication No. 2005-120894, a portion of the oil discharged from the left hand-side subsidiary pump is fed back via a communicating port (3d) and is returned to the intake channel (24). This is one example of an operation when the speed is equal to or above a prescribed speed of revolution. The main pump discharges oil at all times, throughout the speed range.
In Patent Document 1, furthermore, a back pressure chamber (11d) which constitutes a bottom portion of respective vane grooves (11a) is formed in a rotor (11), and a high-pressure chamber (70) (see FIG. 2) is formed between a bottom wall (2c) which is a portion of a cover (2) and a second side plate (14), whereby a portion of the operating oil discharged from the pump chamber (18) is introduced therein via respective second back pressure supply channels (71, 72) formed in the second side plate (14).
After operating the vane pump (P), the operating oil in the high-pressure chamber (70) is guided via the second back pressure supply channels (71, 72) to the back pressure chamber (11d) as back pressure operating oil, and due to the back pressure of this back pressure operating oil acting on the back surface (12e), which is the end surface of the inner end of the vanes (12), the vanes (12) are pressed radially outwards inside the vane grooves (11a), and the outer ends of the vanes (12) are pressed against the cam surface (17).
Consequently, the outer circumference front ends of the vanes (12) are pressed strongly by the cam ring (10), and therefore oil leaks are decreased, and consequently the discharge performance is improved. Via openings (63a, 63b), the first back pressure supply channel (62) communicates with a high-pressure chamber 70 via second back pressure supply channels (71, 72) and the back pressure chamber 11d, and furthermore a back pressure operating liquid is supplied to the back pressure chamber (11d) which corresponds to a vane (12) in a transition range from the discharge range to the
[Patent Document 1] Japanese Patent Application Publication No. 2005-120894